LIST OF ILLUSTRATIONS 



FIG. 



1. A bean placed in water, showing successive stages in the 



process of wrinkling ........ 3 



2. Seeds placed in hot water to find out where the openings are 4 



3. Three rows of corn planted at the same time, each grain 



being half buried in the moist soil 5 



4. A way to test the swelling force of seeds .... 7 



5. The swelling force of seeds . . . . . . . 8 



6. A squash seed showing the " peg " 8 



7. Roots of an oak tree ........ 11 



8. Root hairs of radish 13 



9. Seed covers floating on water 15 



10. A young plant 16 



11. A glacier or river of ice 19 



12. Valley and stream 21 



12 a. A cut across a valley 22 



13. Sloping masses of rock at the base of cliffs .... 24 



14. Diagram showing how much deeper plant roots can feed in 



arid soils than in humid soils ...... 31 



15. Irrigation ditch 35 



15 a. How water changes the barren sage country to orchards 



arid fertile fields 36 



16. Building an irrigation dam in Arizona 37 



17. Faulty methods of cultivation (the land is fast being cut up 



and washed away by the rains) 38 



18. Rich soil is washed away by the rains, and low walls are 



built in the river bed to catch it 39 



IS a. Pasture land in Arizona in its natural condition . . 40 



186. This was once pasture land like that shown in Figure 18 a 41 



xiii 



